A conventional system provides both real-time video and real-time layered graphics in a layered display. Each layer of the layered graphics is generated by its own separate graphical pipeline. The number of graphical layers that can overlay a position on the screen (e.g., a single video pixel) is therefore limited by the number of separate graphical pipelines that can be implemented in hardware.
The conventional system may suffer from one or more of the following disadvantages. For example, such a configuration uses a substantial amount of chip space since a graphical pipeline must be added for each desired graphical layer. The addition of more graphical pipelines also increases the cost of producing the chip.
Furthermore, a plurality of graphical pipelines in concurrent use may exceed the available bandwidth. Each graphical pipeline may have substantial bandwidth requirements, especially where each graphical pipeline is providing a full-screen, real-time graphical surface. However, a plurality of graphical pipelines each concurrently providing a respective full-screen, real-time graphical surface would overload a conventional system. For example, the real-time nature of the graphical demands may create a memory bottleneck, thereby resulting in a failure (e.g., visual and audio display defects due to insufficient memory access when needed). This bandwidth concern also may limit the number of graphical surfaces that may be displayed or the number of graphical pipelines that may be implemented concurrently. Such bandwidth concerns are further exacerbated when multiple video output streams (e.g., independent video output streams) are desired such as, for example, in a multiple video output set top box environment.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of ordinary skill in the art by comparison of such systems with aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.